RSSArchive for June, 2012

Black hole to destroy cloud

  • Giant gas cloud about to enter black hole
  • The black hole is at the centre of our galaxy
  • Astronomers to watch it happen in 2013

THE BLACK HOLE AT THE CENTRE of the our galaxy, formally known as Sagittarius A* – pronounced Sagittarius A star – is about to unleash its destructive power. By mid-2013, a gas cloud is expected to pass in its vicinity at a distance of only 36 light-hours (equivalent to 40,000,000,000 km), which is extremely close in astronomical terms. The cloud will be ripped apart.

For the past 20 years, Stefan Gillessen, an astrophysicist at the Max Planck Institute for Extraterrestrial Physics in Munich, Germany, has been studying the black hole. “So far there have been only two stars [we have seen] that came that close to Sagittarius A*”, he says. “They passed unharmed, but this time will be different: the gas cloud will be completely ripped apart by the tidal forces of the black hole.”

A black hole is what remains after a supermassive star dies. When the “fuel” of a star runs low, it will first swell and then collapse to a dense core. If this remnant core has more than three times the mass of our Sun, it will transform to a black hole.

Direct observations of such black holes are impossible because they are coal-black and do not emit light or matter. But astronomers can identify a black hole indirectly due to the affect it has on objects in its vicinity.

So-called supermassive black holes are the largest type. Their mass equals hundreds of thousands to a billion times the mass of our Sun. The centres of all galaxies are thought to contain supermassive black holes. But their origin is not fully understood and astrophysicists can only speculate as to what happens inside them. Hence the imminent collision is of great interest, as it should provide some new insights.

Reinhard Genzel (European Southern Observatory) leads the team of astronomers that discovered the cloud and studied its trajectory. According to their observations, its speed has nearly doubled in the last seven years, reaching more than 8 million km/h.

The cloud’s edges have already started to shred and it is expected to break up completely over the coming months. As it nears the collision, the cloud is expected to get much hotter and probably emit X-rays.

Adapted from information issued by the Max Planck Institute for Extraterrestrial Physics.

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Sentinel telescope to protect Earth

IN A PRESS CONFERENCE at the California Academy of Sciences Thursday Morning (US time), the B612 Foundation unveiled its plans to build, launch, and operate the first privately funded deep space mission.

Called Sentinel, the a space telescope will be placed in orbit around the Sun, ranging up to 270 million kilometres from Earth, for a mission of discovery and mapping.

The Foundation leadership and technical team includes some of the most experienced professionals in the world to lead this effort.

“The orbits of the inner Solar System where Earth lies are populated with a half million asteroids larger than the one that struck Tunguska (June 30, 1908), and yet we’ve identified and mapped only about one percent of these asteroids to date, said Ed Lu, space shuttle, Soyuz, and International Space Station astronaut, now Chairman and CEO of the B612 Foundation.

The asteroid that entered Earth’s atmosphere over Tunguska, Russia, was only about 40 metres across (less than the length of an Olympic swimming pool) yet destroyed an unpopulated area roughly the size of the San Francisco Bay area.

“During its 5.5-year mission survey time, Sentinel will discover and track half a million near Earth asteroids, creating a dynamic map that will provide the blueprint for future exploration of our Solar System, while protecting the future of humanity on Earth,” says Lu.

Trees flattened at Tunguska in 1908

A 40-metre-wide meteroid exploded in the air over Tunguska, Russia, in 1908, flattening over 2,000 square kilometres of forest.

Spotting dangerous asteroids

Asteroids are a scientific and economic opportunity in that they contain the original building blocks of the Solar System. They are targets for future human exploration, and may contain valuable raw materials for mining.

But these asteroids are also a threat in that they can pose great risk to humanity here on Earth. Taking advantage of these opportunities and dealing with these threats require not only knowing where each of these individual asteroids is now, but also projecting where they will be in the future.

“For the first time in history, B612’s Sentinel mission will create a comprehensive and dynamic map of the inner Solar Systemin which we live—providing vital information about who we are, who are our neighbours, and where we are going,” says Rusty Schweickart, Chairman Emeritus of B612, and Apollo 9 astronaut.

Diagram of the Sentinel telescope

The solar-powered Sentinel telescope will be equipped with a special camera to spot asteroids.

“We will know which asteroids will pass close to Earth and when, and which, if any of these asteroids actually threaten to collide with Earth,” adds Schweickart. “The nice thing about asteroids is that once you’ve found them and once you have a good solid orbit on them you can predict a hundred years ahead of time whether there is a likelihood of an impact with the Earth.”

Sentinel to launch in five years

Advances in space technology, including advances in infrared sensing and on-board computing, as well as low-cost launch systems, have opened up a new era in exploration where private organisations can now carry out grand and audacious space missions previously only achievable by governments.

The B612 Foundation is working with Ball Aerospace, Boulder, Colorado, which has designed and will be building the Sentinel Infrared (IR) Space Telescope with the same expert team that developed the Spitzer and Kepler space telescopes. It will take approximately five years to complete development and testing to be ready for launch in 2017-2018. The launch vehicle of choice is the SpaceX Falcon9.

Sentinel will scan the entire night half of the sky every 26 days to identify every moving object, with repeated observations in subsequent months. Data collected by Sentinel will be sent back to the Earth via NASA’s Deep Space Network, which also will be used for tracking and navigation.

More information: B612 Foundation

Adapted from information issued by the B612 Foundation.

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Partial lunar eclipse on Monday

The Moon, partially eclipsed.

Monday, June 4, will see a partial eclipse of the Moon take place.

FOR THOSE WHO ARE ON GOOD TERMS with the weather gods, on Monday, June 4, there will be a partial eclipse of the Moon to enjoy.

A lunar eclipse happens when the Moon moves into the Earth’s shadow. If it goes through the middle of the shadow, it is a total lunar eclipse. If it “cuts the corner” of the shadow, we get a partial eclipse.

There are usually two or three lunar eclipses each year, but they’re not always visible from the same place. From any particular spot on Earth, you might see one or two per year.

The Moon will begin to move into the darkest part of Earth’s shadow at 8:00pm, Sydney time on Monday, June 4. In Perth, it will already be underway by the time the Moon rises. Mid-eclipse will be at 9:00pm Sydney time, and the whole thing will be over by 10:05pm, Sydney time.

At mid-eclipse, about 40% of the Moon’s diameter will be covered by Earth’s shadow – it might even go a reddish colour from sunlight bent through Earth’s atmosphere. Then the Moon will slowly move out of the shadow.

As long as the weather is clear, you won’t have any difficulty spotting the Moon and the eclipse. You won’t need a telescope or binoculars to see it –  just your own eyes are enough. And unlike solar eclipses, lunar eclipses are safe to watch.

They also happen slowly, so the best idea is to go outside every 15 minutes or so and see how it has changed.

Here’s a video from NASA that shows what stargazers in North America can expect to see:

After this, the next big eclipse for Australians will be a total eclipse of the Sun on the morning of Nov 14, 2012 – the last one to be seen in Australia until the year 2028! Totality will be seen only along a narrow swathe of far north Queensland near Cairns. Everyone else will see a partial eclipse.

Story by Jonathan Nally, editor, SpaceInfo.com.au

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